Signs of Rectal Cancer: 4 Symptoms to Recognize Rectal Cancer

Rectal cancer is a dangerous gastrointestinal cancer, but it is often detected late because the initial symptoms are easily mistaken for hemorrhoids, constipation, or common digestive disorders. According to medical statistics, if detected in the early stages, the 5-year survival rate can be up to about 90%. Conversely, when the disease progresses to a late stage, treatment becomes much more difficult and costly.

Many people often ignore the signs of rectal cancer such as bloody stools, changes in bowel habits, prolonged abdominal pain, or unexplained weight loss. This complacency allows the disease to silently develop for a long time before being diagnosed.

The article below will help you recognize the early symptoms of rectal cancer, understand important warning signs, and know when to seek screening. Timely detection of the disease not only helps increase treatment effectiveness but can also protect your health and life in the future.

Part 1: How to recognize early rectal cancer

Symptom 1: Prolonged bowel movement disorders

Monitor chronic diarrhea or constipation

Unusual changes in bowel habits are one of the common but easily overlooked signs of rectal cancer. If this condition lasts for many weeks and is not related to diet or common illnesses, you should pay special attention.

• Frequent, prolonged diarrhea with no clear cause.
• Persistent constipation that is difficult to improve even after dietary changes.
• Sudden changes in bowel habits compared to before.
• Alternating bouts of diarrhea and constipation.

Pay attention to the feeling of incomplete bowel evacuation

Many people with colorectal cancer often feel that there is still stool in their intestines even after having a bowel movement. This condition can occur frequently and affect daily life.

• Always feel the urge to have a bowel movement even after just going.
• Feeling that the bowel has not been completely emptied.
• Having to go to the bathroom multiple times a day but still not feeling comfortable.

Do not ignore discomfort during bowel movements

When a tumor develops in the rectum, patients may experience pain or discomfort during bowel movements. This is one of the symptoms of rectal cancer that needs to be carefully monitored.

• Feeling of pressure or fullness in the anal-rectal area.
• Pain or discomfort during bowel movements.
• Feeling of an obstruction or blockage as stool passes.
• Symptoms are prolonged and progressively worsen over time.

If the above signs appear continuously for many weeks, especially when accompanied by bloody stools, prolonged abdominal pain, or unusual weight loss, you should proactively visit a gastroenterologist for evaluation and timely rectal cancer screening.

Symptom 2: Blood in stool requires caution

Observe bloody stools

Bloody stools are one of the common signs of rectal cancer in the early stages. However, many people often mistake this symptom for hemorrhoids, leading to complacency and missing the opportunity for early detection.

• Bright red blood appears on stool or toilet paper after a bowel movement.
• Blood is dark red or almost black, indicating that the blood may have been in the digestive tract for some time.
• Recurrent bleeding with no clear cause.

Pay attention to changes in stool shape

The growth of a tumor in the rectum can narrow the bowel lumen, causing the stool shape to change unusually. This is one of the symptoms of rectal cancer that needs to be carefully monitored.

• Stool is small, flat, or thinner than normal for a long period.
• Stool size changes significantly compared to before.
• Unusual stool shape persists and is not related to diet or current medications.

Do not underestimate prolonged signs

Although bloody stools can result from various causes, when the symptom persists or is accompanied by other unusual signs, the risk of serious medical conditions increases.

• Bloody stools accompanied by abdominal pain or discomfort in the lower abdomen.
• Prolonged changes in bowel habits.
• Feeling of incomplete bowel evacuation.
• Fatigue, anemia, or unexplained weight loss.

Since this is one of the most common early warning signs of rectal cancer, you should proactively seek medical attention if you notice blood in your stool or any unusual changes in stool shape and size that persist for several weeks.

Symptom 3: Prolonged abdominal pain and rectal pain

Note pain in the abdomen or rectum

Persistent abdominal pain or discomfort in the rectal area can be one of the signs of rectal cancer that needs attention. Many people often dismiss this as a common digestive disorder, overlooking early warning signs.

• Dull or cramping pain in the lower abdomen.
• Feeling of pain, pressure, or discomfort in the rectal area.
• Pain attacks occur frequently and last for many weeks.
• The intensity of pain tends to gradually increase over time.

Pay attention to bloating and pain due to gas accumulation

Changes in bowel activity can cause prolonged bloating and discomfort. This is a common symptom in many digestive diseases, including colorectal cancer.

• Frequent bloating even with normal eating habits.
• Pain due to gas accumulation in the intestines.
• Presence of cramps or spasms in the abdomen.
• Feeling of prolonged abdominal distension with no clear cause.

Unusual feeling of fullness or abdominal distension

Some patients may feel their abdomen is always full or bloated even when they haven't eaten or have eaten very little. This condition can affect appetite and daily quality of life.

• Always feeling heavy or bloated.
• Getting full faster than usual when eating.
• Feeling of prolonged abdominal fullness for many hours.
• Abdominal discomfort even when not having recently eaten.

Monitor accompanying symptoms

When abdominal pain or bloating occurs with other unusual signs, the risk of serious medical conditions is higher and requires early examination.

• Prolonged changes in bowel habits.
• Bloody stools or blood in the stool.
• Unexplained weight loss.
• Prolonged fatigue or anemia.

If abdominal pain, rectal pain, bloating, or an unusual feeling of fullness persists for many weeks without improvement, you should proactively visit a gastroenterologist for examination and timely rectal cancer screening.

Symptom 4: Loss of appetite and prolonged fatigue

Monitor unusual loss of appetite

Prolonged loss of appetite is one of the signs of rectal cancer that can appear when the body is experiencing serious problems. Many people often assume this is just a symptom of stress or normal fatigue and do not pay attention to monitoring it.

• Eating less than usual for a long period.
• No longer feeling hungry when eating.
• Getting full quickly even after eating a small amount of food.
• Frequently skipping meals or not wanting to eat.

Pay attention to unexplained weight loss

When the body does not receive enough energy or a medical condition affects nutrient absorption, weight can decrease significantly without intention.

• Weight loss despite not dieting or increasing exercise.
• Clothes becoming looser in a short period.
• Continuous weight loss with no identifiable cause.
• Weight loss accompanied by unusual digestive symptoms.

Recognize feelings of fatigue and lack of energy

Many people with colorectal cancer often feel sluggish and lack vitality even after adequate rest. This condition may be related to anemia or a decline in health caused by the disease.

• Frequently feeling exhausted during daily activities.
• Difficulty concentrating at work or studying.
• Lack of energy despite getting enough sleep.
• Prolonged fatigue that does not improve over time.

Proactively seek medical examination when there are many unusual signs

Each individual symptom can stem from various causes. However, when multiple signs appear simultaneously, the risk of serious medical conditions is higher.

• Prolonged loss of appetite.
• Unexplained weight loss.
• Frequent fatigue.
• Changes in bowel habits.
• Bloody stools or blood in the stool.
• Abdominal pain or discomfort in the rectal area.

If you experience many of the above-mentioned symptoms of rectal cancer or if the symptoms are increasingly severe, you should proactively visit a medical facility for examination and early screening. Early detection of the disease can help improve treatment effectiveness and significantly enhance health prognosis.

Part 2: How to screen for colorectal cancer

Step 1: Fecal occult blood test

Perform fecal occult blood test (FOBT)

The fecal occult blood test is a screening method that helps detect very small amounts of blood in the stool that are invisible to the naked eye. This is one of the tests commonly used to aid in the early detection of rectal cancer and other gastrointestinal diseases.

• The patient will be asked to provide a stool sample according to the instructions of medical staff.
• Stool collection is simple, non-invasive, and can be done quickly.
• The test helps detect microscopic bleeding in the intestines even before clear symptoms appear.

Adhere to pre-sample collection instructions

Depending on the type of test ordered, your doctor may ask you to follow certain instructions before sample collection to ensure more accurate results.

• Restrict or avoid certain foods for a few days before the test.
• Inform your doctor about any medications or supplements you are currently taking.
• Follow the correct sample collection procedure as instructed by the medical facility.

The stool sample will be analyzed in the laboratory

After collection, the stool sample will be sent to the laboratory to check for the presence of occult blood. The test results will help the doctor assess the risk of developing colorectal related diseases.

• Samples are processed and analyzed using specialized methods.
• Results are usually available after a period specified by the testing facility.
• If abnormalities are found, the doctor may order additional specialized tests.

Correctly understand the meaning of test results

The fecal occult blood test is an effective screening tool, but it cannot definitively confirm whether a person has colorectal cancer.

• A positive result indicates blood in the stool and requires further investigation.
• A negative result does not completely rule out the risk of disease.
• The doctor may recommend a colonoscopy or other tests to determine the exact cause.

For individuals with signs of rectal cancer, a family history of the disease, or those in a high-risk group, regular fecal occult blood testing can help detect abnormalities early and increase the chances of effective treatment.

Step 2: Digital rectal exam

Perform a digital rectal exam (DRE)

A digital rectal exam is a simple examination method that helps doctors detect abnormalities in the rectum and lower abdominal area. This is an initial assessment step often ordered when a patient has signs of rectal cancer or symptoms related to the digestive tract.

• The doctor uses medical gloves and directly examines the rectal area.
• Simultaneously evaluates the abdominal area for abnormal signs.
• The purpose is to detect tumors, hard lumps, or unusual changes in tissue structure.

Early detection of abnormal masses

If suspicious signs are noted during the examination, the doctor may order additional specialized tests to determine the cause.

• Check for the presence of tumors or hard lumps in the rectum.
• Assess the degree of abnormality of tissue and mucosa.
• Support guiding the next diagnostic steps.

More specialized tests may be needed

A digital rectal exam is only an initial screening step and cannot replace specialized diagnostic methods.

• Colonoscopy helps directly observe the inside of the large intestine and rectum.
• Sigmoidoscopy may be ordered to examine the suspected area.
• Biopsy may be performed if an abnormal lesion is detected.

The examination process is quick

Many people feel anxious or embarrassed before undergoing the examination. However, this is a common medical procedure, which is quick and usually only causes slight discomfort for a short time.

• The examination usually only takes a few minutes.
• The doctor will explain the procedure before performing it.
• The patient can communicate if they feel uncomfortable during the examination.

Do not overlook regular screening

Some cases of early-stage rectal cancer may not cause any obvious symptoms. Therefore, regular screening plays an important role in early disease detection.

• Individuals aged 45 and older should discuss appropriate screening plans with their doctor.
• People with a family history of colorectal cancer may need earlier screening.
• Regular colonoscopy helps detect polyps or pre-cancerous lesions before they develop into disease.

Proactively seeking examination and screening at the right time is one of the most effective ways to detect rectal cancer early, thereby improving treatment success rates and protecting long-term health.

Step 3: Sigmoidoscopy

Perform sigmoidoscopy when indicated

Sigmoidoscopy is a method that allows doctors to directly visualize the inside of the rectum and the lower part of the colon. This test is commonly used to aid in the early detection of rectal cancer, colorectal polyps, and other abnormalities of the digestive tract.

• The doctor uses a thin, flexible tube with a camera and light source at the end.
• The device is gently inserted through the anus to examine the lining of the rectum and sigmoid colon.
• The images obtained will be displayed on a screen for the doctor to evaluate lesions or abnormalities.

Bowel preparation before colonoscopy

For accurate examination results, the colon needs to be cleaned before the procedure. Remaining stool can obscure small lesions and affect diagnostic capability.

• Follow your doctor's dietary instructions before the day of the colonoscopy.
• Use bowel cleansing medication if prescribed.
• Drink enough water as instructed to support the preparation process.

Helps detect abnormalities in the colorectal region

Sigmoidoscopy allows the doctor to directly observe abnormal changes that are difficult to detect with conventional tests.

• Detect colorectal polyps.
• Identify inflamed, ulcerated, or abnormally bleeding areas.
• Look for suspicious signs of colorectal cancer.
• Assist in obtaining biopsy samples if necessary.

The procedure usually does not take long

Many people worry about discomfort during endoscopy. However, the procedure is usually relatively quick and performed by a specialized medical team.

• The procedure time is usually shorter than a full colonoscopy.
• Temporary feelings of bloating or fullness may occur during the examination.
• In some cases, sedatives are not required.

Discuss with your doctor if you wish to reduce discomfort

The level of discomfort during endoscopy can vary from person to person. If you feel anxious, you should discuss it with your doctor beforehand to receive appropriate advice.

• Ask about the procedure in detail before the endoscopy.
• Discuss the possibility of using sedatives if needed.
• Fully comply with instructions before and after the procedure.

Sigmoidoscopy is a useful method for early detection of signs of rectal cancer and lower gastrointestinal diseases. Performing the examination as directed by a doctor can help diagnose the disease in a timely manner and improve treatment effectiveness.

Step 4: Colonoscopy

Perform a colonoscopy for comprehensive examination

Colonoscopy is one of the most effective methods for early detection of rectal cancer and abnormalities in the lower gastrointestinal tract. This procedure allows the doctor to directly observe the entire rectum and colon, thereby accurately assessing the patient's health status.

• The doctor uses a flexible endoscope with an attached camera and light source.
• The device is inserted through the anus to examine the inside of the colon and rectum.
• Images are transmitted directly to a screen, helping to detect small lesions that other tests might miss.

Helps detect and manage abnormal lesions

In addition to aiding diagnosis, colonoscopy also allows the doctor to intervene immediately upon detecting suspicious abnormalities.

• Detect colorectal polyps.
• Look for signs of colorectal cancer.
• Identify areas of inflammation, ulceration, or abnormal bleeding.
• Polyps can be removed or tissue samples can be taken for specialized biopsy.

Patients are often sedated

To reduce discomfort during colonoscopy, many medical facilities use sedation or short-term anesthesia.

• Helps the patient relax and feel more comfortable.
• Reduces pain or discomfort during the procedure.
• The examination process is usually gentler and more convenient.

Bowel cleansing before colonoscopy

Preparation before colonoscopy plays a very important role in the accuracy of the results. A clean colon helps the doctor clearly observe the mucous membrane and detect small lesions.

• Follow your doctor's dietary instructions before the day of the colonoscopy.
• Use bowel cleansing medication as prescribed.
• Drink the recommended amount of water during preparation.
• Comply fully with instructions from the medical facility to avoid having to repeat the colonoscopy.

Early screening helps increase successful treatment chances

Many cases of early-stage rectal cancer do not show obvious symptoms. Therefore, colonoscopy is considered an important tool for detecting the disease before signs become severe.

• Increases the chance of successful treatment.
• Reduces the risk of complications and recurrence.
• Limits the need for complex treatment methods.
• Improves quality of life and long-term prognosis.

If you are in a high-risk group, have a family history of colorectal cancer, or are experiencing symptoms such as bloody stools, changes in bowel habits, prolonged abdominal pain, or unexplained weight loss, talk to your doctor about colonoscopy for timely screening and diagnosis.

Step 5: Virtual Colonoscopy

Consider virtual colonoscopy for less invasiveness

Virtual colonoscopy is a screening method that uses computed tomography (CT) technology combined with X-rays to create detailed images of the colon and rectum. This is a suitable option for some people who want to be screened for rectal cancer but do not want to undergo traditional colonoscopy or are not eligible for colonoscopy due to other health issues.

• Does not use a long endoscope to examine the entire colon.
• Images are recorded from outside the body using a modern scanning system.
• Helps detect polyps or abnormal masses in the colorectal region.

Bowel cleansing is still needed before the examination

Although less invasive than conventional colonoscopy, patients still need thorough bowel preparation to ensure accurate results.

• Follow the dietary instructions provided before the examination day.
• Use bowel cleansing medication as prescribed by the doctor.
• Ensure the colon is free of stool or food residue that could obscure images.

Can detect early signs of abnormality

Virtual colonoscopy helps doctors assess the internal condition of the colorectum and aids in early detection of many dangerous diseases.

Detect colorectal polyps.

Identify suspicious tumors.

Supports early screening for colorectal cancer.

Evaluates abnormal changes in the colon structure.

May require conventional colonoscopy afterwards

One limitation of virtual colonoscopy is that it cannot collect tissue samples or remove polyps during the examination.

• If abnormal lesions are detected, the doctor will usually recommend a standard colonoscopy.
• Traditional colonoscopy allows for polyp removal or biopsy for accurate diagnosis.
• Additional examination helps determine the nature of lesions found on CT images.

Check costs before proceeding

The cost of virtual colonoscopy may vary depending on the medical facility, region, and insurance coverage policies.

• It is advisable to discuss the total cost of the procedure with the healthcare provider beforehand.
• Find out about health insurance or medical insurance benefits if you have them.
• Prepare a suitable financial plan before undergoing the test.

Virtual colonoscopy is a modern screening method that helps early detect signs of rectal cancer and colorectal abnormalities. However, patients should discuss with their doctor to choose the most suitable examination method for their health condition and risk of disease.

Step 6: Double-Contrast Barium Enema

Consider double-contrast barium enema if colonoscopy is not possible

A double-contrast barium enema is a method to screen for rectal cancer and colorectal abnormalities when a patient cannot undergo a colonoscopy due to health issues or medical contraindications.

• This method uses a barium solution combined with X-rays to examine the colorectum.
• The images obtained help the doctor assess the internal structure of the large intestine.
• It can help detect tumors, polyps, or abnormal narrowings.

Barium solution helps visualize the colorectum clearly

Before the X-ray, the patient will have a barium solution introduced into the colon via an enema. This contrast agent helps highlight the intestinal lining on the X-ray film.

• Barium coats the surface of the colorectal lining.
• This makes abnormalities easier to identify on diagnostic images.
• Helps the doctor assess the shape and structure of the colon.

An alternative option in some cases

For those who cannot undergo a colonoscopy, this can be an alternative solution to initially assess the colorectal condition.

• Suitable for some patients at high risk during colonoscopy.
• May be indicated when colonoscopy is not feasible or cannot be completed.
• Helps screen for diseases related to the colorectum.

Has limitations compared to colonoscopy

Although useful in some cases, a double-contrast barium enema does not provide as detailed images as a colonoscopy and does not allow for direct intervention.

• Cannot take tissue biopsy samples.
• Cannot remove polyps during the examination.
• Accuracy for small lesions may be lower than colonoscopy.

May require additional tests

If the results of the scan reveal abnormalities, the doctor will often recommend more specialized methods to confirm the diagnosis.

• Colonoscopy to directly visualize the lesion.
• Tissue biopsy if cancer is suspected.
• Additional imaging or blood tests if necessary.

A double-contrast barium enema is a supportive option in screening for colorectal cancer, especially for those who cannot undergo colonoscopy. However, patients should consult their doctor to choose the most suitable examination method for their health condition and risk of disease.

Part 3: Methods for Diagnosing Rectal Cancer

Method 1: Discuss screening results with your doctor

Thoroughly understand the results after screening

After completing the tests or screening methods for rectal cancer, the doctor will analyze the results and explain your health status in detail. This is an important step to determine whether further monitoring or specialized diagnostic methods are needed.

• The doctor will evaluate the results based on the tests performed.
• Explain the meaning of any abnormal signs, if present.
• Provide a suitable course of action or follow-up plan.

Results may detect polyps or abnormal cells

Not every abnormality detected is cancer. In many cases, the doctor may find polyps or abnormal cells in the rectum and colorectum.

• Polyps are abnormal growths on the intestinal lining.
• Some polyps are benign but still need to be monitored or removed.
• Abnormal cells can increase the risk of developing cancer in the future.
• Early detection helps reduce the risk of progression to serious illness.

Follow your doctor's follow-up plan

If precancerous lesions or other abnormalities are found, the doctor may suggest follow-up appointments or additional tests.

• Regular follow-up endoscopies as scheduled.
• Biopsy if accurate assessment of the lesion's nature is needed.
• Monitor changes in polyps or abnormal mucosal areas.
• Actively report any new symptoms.

Early detection helps improve treatment effectiveness

One of the greatest benefits of screening is the ability to detect early-stage rectal cancer, when the disease has not spread widely and treatment is often more effective.

• Increased chances of successful treatment.
• Reduced risk of complications and recurrence.
• Limited need for complex treatment methods.
• Improved quality of life and long-term prognosis.

Do not miss follow-up appointments

Even if initial results do not reveal cancer, regular health monitoring is still essential, especially for those with high-risk factors.

• Family history of colorectal cancer.
• Previous detection of colorectal polyps.
• Frequent symptoms such as bloody stools, changes in bowel habits, or prolonged abdominal pain.
• Individuals aged 45 and above need to undergo screening as recommended by their doctor.

Open communication with your doctor and understanding your test results will help you be more proactive in preventing, monitoring, and early detecting signs of rectal cancer, thereby increasing the chances of effective treatment and protecting your long-term health.

Method 2: Determine the stage of rectal cancer

Understand the disease stage after diagnosis

After confirming a diagnosis of rectal cancer, the doctor will conduct specialized tests to determine the disease stage. Staging helps assess the extent of tumor spread, predict prognosis, and choose the most appropriate treatment method.

• Additional imaging, blood tests, or biopsies may be required.
• The results will indicate the extent of cancer cell invasion.
• This is a crucial basis for developing a personalized treatment plan.

Stage 1: Cancer is localized

In the earliest stage, cancer cells have just appeared in the lining or wall of the rectum and have not spread to other areas.

• The tumor is confined to the rectum.
• Has not invaded lymph nodes or distant organs.
• Treatment prognosis is usually very good if detected early.

Stage 2: Cancer has spread beyond the rectal wall

The tumor has grown deeper and may have spread to adjacent tissues or structures, but has not metastasized to lymph nodes.

• A higher level of invasion than Stage 1.
• May affect tissues near the rectum.
• Requires aggressive treatment to prevent disease progression.

Stage 3: Cancer has spread to lymph nodes

At this stage, cancer cells have migrated to regional lymph nodes near the rectum.

• Lymph nodes show cancer cells.
• Higher risk of disease spread.
• Often requires a combination of treatments for effective disease control.

Stage 4: Metastatic Cancer

This is the most advanced stage of rectal cancer, when cancer cells have spread to other organs in the body.

• The liver is one of the most common sites of metastasis.
• Additionally, cancer can spread to the lungs or other organs.
• Treatment focuses on controlling the disease, extending survival time, and improving quality of life.

Disease Stage Directly Affects Treatment Method

After determining the stage, the doctor will propose a treatment plan suitable for each patient's specific condition.

• Surgery may be indicated to remove the tumor.
• Chemotherapy helps kill or control cancer cells.
• Radiation therapy is often used in some cases to shrink tumors or reduce the risk of recurrence.
• Targeted therapy drugs or immunotherapy may be considered in some suitable patients.

Although rectal cancer is a serious disease, early detection often offers a significantly higher chance of successful treatment. Therefore, regular screening and adherence to the doctor's treatment regimen are important factors in improving prognosis and quality of life.

Method 3: Regular Rectal Cancer Screening

Maintain screening even if results are normal

If screening results do not detect rectal cancer, you should still continue screening as recommended by your doctor. Many cases of the disease develop silently for a long time without clear symptoms, so regular check-ups play a very important role.

• Do not be complacent if no abnormal signs appear yet.
• Regular screening helps detect precancerous lesions early.
• The earlier it is detected, the higher the chance of successful treatment.

Pay special attention if you belong to a high-risk group

Some individuals have a higher risk of developing colorectal cancer than the general population and need closer monitoring.

• People aged 45 and older should discuss an appropriate screening plan with their doctor.
• Have a family history of colorectal cancer or colorectal polyps.
• Previously detected polyps or precancerous lesions.
• Suffer from chronic inflammatory bowel disease or have other risk factors as assessed by a doctor.

Implement personalized screening schedules

Not everyone needs to be checked at the same frequency. The time between screenings will depend on age, medical history, risk factors, and previous test results.

• Some people need more frequent check-ups to monitor detected abnormalities.
• Some low-risk cases may be screened at longer intervals.
• The doctor will provide a suitable examination schedule for each individual.

Screening is an effective way to protect long-term health

The goal of screening is not only to detect cancer but also to find precancerous lesions before they develop into dangerous diseases.

• Early detection and timely treatment of polyps.
• Reduced risk of progression to invasive cancer.
• Reduced severe complications in the future.
• Improved quality of life and longevity.

Actively monitor for abnormal signs

In addition to regular screening, you should also pay attention to changes in your body to seek medical attention promptly when necessary.

• Blood in the stool or bloody stools.
• Prolonged changes in bowel habits.
• Abdominal pain or discomfort in the rectal area.
• Unexplained weight loss.
• Prolonged fatigue or lack of energy.

Adhering to the recommended schedule for rectal cancer screening is one of the most effective measures to detect the disease early, increase the chance of successful treatment, and protect long-term health.

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Content edited by: Rene Lee Nguyen.

Information consulted and verified by expert: Isabella Moore.